Wall Street edges up as Canada takes trade spotlight

NEW YORK (Reuters) - The S&P 500 and the Nasdaq edged up to record highs for the third consecutive session on waning trade jitters that have vexed the markets for much of the year.

On the heels of the United States-Mexico agreement to overhaul the North American Free Trade Agreement (NAFTA), focus shifted to United States' trading partner to the north as Canada's top trade negotiator joined her Mexican and U.S. counterparts in Washington in a bid to remain in the trilateral pact.

All three major U.S. indexes were marginally up in a session of back-and-forth trading as investors debated whether to take profits or ride the market's momentum.

"People trying to figure out whether it pays to stay in (the market) or would it be prudent to take profits now that we got the bump on recent positive trade news," said Chuck Carlson, chief executive officer at Horizon Investment Services in Hammond, Indiana. "Is the next news on the trade front going to be negative? Should they sell or ride the momentum right now?"

Luxury retailer Tiffany & Co reported better-than-expected second-quarter results and raised its full-year profit forecast. The stock trimmed early gains, and is now up 0.1 percent.

Sears Holding Corp shares jumped 13.5 percent as its Auto Center partnership with Amazon.com expanded, its services now available nationwide. The partnership was first announced in May.